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Currently, Xanthomonas axonopodis is one of the main foliar pathogens for Eucalyptus spp. in Brazil. It induces leaf blight and defoliation of seedlings in the nursery and young plants in the field. However, little is known about the favorable conditions for infection. The establishment and development of bacterial leaf blight caused by X. axonopodis in eucalyptus was studied for different leaf ages, temperatures and leaf wetness durations. Disease severity increased with leaf age, and the highest severity was observed on the fourth pair of completely expanded leaves (from the apex to the base). A higher level of bacterial colonization was also observed on the fourth pair of leaves quantified as bacterial cells/cm 2 of leaf area. Twelve hours of free water on the leaf surface, prior to inoculation, was essential to promote a severe infection. However, with the increase in the leaf wetness duration, a decrease in disease severity was observed. The optimal temperature for disease development was 26-30ºC.

Genus Atta includes some of the most important Formicidae leaf cutter ants which cause extensive damage to the eucalyptus plantations. Atta sexdens rubropilosa Forel, one of the chief pests in Brazilian reforestation, can restrict and reduce forest productivity by its intense and constant leaf-cutting activities on plants at all stages. Therefore, the demand for new products to control A. sexdens rubropilosa indicates the study of the utilization of the dry powder formulation of diatomaceous earth (DE) against this pest in the eucalyptus cultivars. The study was conducted using 120 colonies of A. sexdens rubropilosa in Eucalyptus grandis Hill ex. Maiden x Eucalyptus urophylla Blake (Myrtaceae) (urograndis) stand. The randomized block experimental design was used with six treatments (1, 10, 25, and 50 g/m2 of DE, 6.0 g/m2 sulfluramid bait per square meter of loose soil, and the control) with five replications, each with four colonies of this ant. Diatomaceous earth was applied to the active A. sexdens rubropilosa ant holes, and the sulfluramid bait was applied in bulk in a localized manner. The control efficacy of A. sexdens rubropilosa with DE was low, showing values similar to that of the control, and, for this reason, it cannot be used to control this ant. The bait with sulfluramid showed higher efficacy than those of the other treatments.